On an annual basis, tens of millions of people have their blood drawn and tested to provide immediate physiological diagnostics necessary for caregivers to quickly administer the appropriate treatment to the patient. For example, recently, a growing market segment in the area of “near patient” critical care testing specifically addresses enhanced renal function testing. Renal function testing uses a panel of analytes including Na, iCa, Cl, K, HCO3, glucose, lactate, blood urea nitrogen (BUN) and creatinine. The renal panel incorporates three measurements also included in a typical electrolyte/metabolite panel, i.e., creatinine, BUN and measured HCO3.
Acute renal failure (ARF) is defined as an abrupt or rapid decline in renal function. A rise in BUN or creatinine concentrations is usually evidence of ARF. ARF is often transient and completely reversible. HCO3 is a critical parameter in assessing acid-base balance as it relates to renal function. While carbon dioxide (CO2) is the respiratory component in acid-base balance, bicarbonate (HCO3) is the renal component. A blood sample vial, e.g., a Vacutainer® (BD) vial, is used for collecting blood samples from patients.
Often when testing is performed at an outside laboratory, a blood sample is drawn into a heparinized vial, e.g., a Vacutainer® vial, aliquoted into syringe(s), and capped prior to transport or upon receipt in the laboratory. In the operating or emergency room, the sample is prepared in either syringes or poured into smaller cuvettes to accommodate the short sampling probe lengths typical of diagnostic instruments. The short probe length prohibits direct sampling by the diagnostic instrument from an open Vacutainer® vessel. Most multi-use, high volume diagnostic instruments have sample ports that are primarily designed to interface with syringes.
A common sampling error occurs when a diagnostic instrument aspirates a sample from a capped airtight sample vial. As a volume of sample is withdrawn from the sample vial by the diagnostic instrument, a vacuum is introduced in the vial. When the vial is removed from the sample port of the diagnostic instrument, the pressure in the sample pathway of the instrument equilibrates with the atmosphere causing air to rush into the sample pathway and the sample to be pulled further into the sample pathway past the sample sensor area. A sampling error is triggered and the sample is not measured.